Multiple cylinder opposed piston and pumps



Jan. 13, 1948. w, PURDlE 2,434,584

MULTIPLE CYLINDER OPPOSED PISTON AND PUMPS Filed July 6, 1945 3 Sheets-Sheet 1 INVENTOR MW/P/W/ a/WMb/IPMUOZ? Jan. 13, 1948. w, PURDIE 2.434.584

MULTIPLE CYLINDER OPPOSED PISTON AND PUMPS Filed July 6, 1945 3 Sheets-Sheet 2 INVENTOR lVl7/ll9/77l/8/77/770/7PU/U'l6 i/Mu, 0M4 ualf Jan. 13, 1948. w, PURDIE 2,434,584

MULTIPLE CYLINDER OPPOSED PISTON AND PUMPS Filed July 6, 1945 3 Sheets-Sheet 3 INVENTDR Patented Jan. 13, 1948 mmrnma crummn orrosnn ms'roN mm rmurs William Hamilton Purdie. Snnderland, England,

assignor to William Doxiord & Sons Limited,

Sunderland, England, a British company Application July 6, 1945, Serial No. 603,422

Great Britain July 18, 1944 9 Claims. (01. 123-51) This invention relates to arrangements or reciprocating scavenging pumps for six-cylinder single-crankshaft internal-combustion engines, and is particularly applicable, but not limited, to such engines of the opposed-piston type. In such engines of the 2-stroke-cycle single-acting type it has been customary to arrange one, or in certain cases two, scavenging pumps at one end of the engine, such pump or pumps being driven by a suitable crank or cranks on the main shaft. Such an arragnement occupies considerable length and introduces certain balancing problems.

Another known arrangement is to have one scavenging pump centrally situated between two groups of three cylinders, but this also increases the length of the engine, and in order to balance the reciprocating masses of the complete engine efiectively, certain adjustments of the reciprocating masses are required, as described in my Patent 2,398,961, granted April 23, 1946. In both these known arrangements, in order to keep the additional length required to a minimum, the pumps are made of the longest stroke that can be accommodated, but the corresponding reduction in bore reduces the area available for the pump-valves, and so raises the air-velocity through these valves, with resultant air-pumping losses.

A third known arrangement is to have one or alternatively two scavenge-pumps lever driven from the engine-crossheads; these pumps are situated at one side of the engine, but the arrangement introduces unbalanced cross rocking couples.

In none of the above arrangements can the discharges from the scavenging pump cylinders coincide with the scavenging periods of all the working cylinders. There is, therefore, some cyclic variation of scavenge-air pressure in the scavenging air receiver, which results in some cylinders being more eiiectively scavenged than others.

The present invention comprises a six-cylinder single-crankshaft internal-combustion engine of which the crank sequence of the engine units numbered consecutively 1 to 6 is 1-53-62- 4 or alternatively 1--4263'5, wherein three from the centre crossheads of the respective engine units. 4

The scavenge pumps may preferably be of the double-acting type with a relatively large bore and short stroke.

A non-limitative embodiment of the invention as applied to an intemal-combustion engine of the opposed-piston type is hereinafter described with reference to the accompanying drawings wherein: I

Figure 1 shows a longitudinal section of a sixcylinder 2 stroke cycle single-acting singlecrankshaft internal-combustion engine of the opposed-Piston type embodying the invention, while Figure 2 shows a section on the line IIIIin Figure 1.

Figure 3 shows a plan in Figure 1.

The drawings are of a diagrammatic nature of the engine illustrated throughout.

scavenge pumps are driven through laterally ex- I tending levers from the crossheads' of Nos. 1, 2 and 3 engine units respectively or alternatively from the crossheads of Nos. 4, 5 and 6 engine units respectively, thereby ensuring balance of the primary and second forces and couples set up by the reciprocating masses of the engine.

When the invention is applied to opposed-pistonengines the scavenge pumps may be driven According to one embodiment of the invention as applied by way of example to a six-cylinder Z-stroke-cycle single-acting internal-combustion engine of the opposed-piston vertical type, the engine comprises six engine units 1 to 6. The crank sequence of the engine units in the present example is 15--362--4 as illustrated in Figure 2. The engine units 1 to 6 are similar and of known type and the general features of the unit 1 will be briefly described.

The engine unit 1, Figures 1 and 2, comprises a cylinder II in which two pistons I2 and I3 are arranged. The cylinder II has no piston covers. The piston l2 has a short piston rod I! having a centre cross head l5 and this crosshead is connected by a connecting rod [6 to a main crank ll of the single-crankshaft IB mounted in bearings 19. The upper piston l3 carries a pivotallymounted yoke 20 and is guided by guides 2| Figure 2, the endsof the yoke being attached to the upper ends of coupling rods 22 and 23, while at their lower ends these coupling rods are connected to side crossheads 24 and 25. The crossheads 24 and 25 are connected by side connecting rods 26 and 21 to side cranks 28 and 29 of the crankshaft l8. The throw of the main crank H is greater than that of the side cranks 28 and 29 and consequently the stroke of the upper piston i3 is less than that of the lower piston [2.

Fuel e. g. oil, is injected into a combustion space 30 in which air has been compressed during the previous stroke and on the resulting combustion of the fuel, the pistons I 2 and 13 move outwards together until about the end of the stroke the piston 12 uncovers ports 3|, Figure 2, through which scavenging air enters from an air receiver 32, while at the same time the upper piston I3 uncovers exhaust ports 33 leading to an exhaust pipe 34 so that scavenging air from the receiver 32 sweeps out the products of combustion from the cylinder II through the exhaust ports 33 and fills the cylinder with fresh air. On the inwards stroke of the pistons I2 and I3 the ports 3i and 33 are closed by the pistons and the air between the pistons is compressed, and when they again reach the position illustrated in Figures 1 and 2 fuel is injected and ignited so that the pistons I2 and I3 move outwards again and the operations above described are repeated.

The engine units 2 to 6 function in a similar manner to that described for the unit 1."

According to the invention the air receiver 32 is supplied with compressed air by three scavenge pumps 35, I36 and I31 which are driven from the centre crossheads of the engine units 1, 2 and 3 respectively. As the scavenge pumps and their operating mechanisms are identical only the scavenge pump 35 and its operating mechanism will be described.

The scavenge pump 35 has a cylinder 36 of which the bore is comparatively large and in this cylinder is arranged a piston 31 or relatively short stroke which is connected to a piston rod 38. In the cylinder 36 are arranged suction valves 39 and delivery valves 40. The suction valves 39 are connected to an air intake 4| which is fitted with a si.encer 42 while the delivery valves 40 are connected to a delivery pipe 43. The suction and delivery valves 39 and 43 are arranged in separate compartments in the pump and passages 44, Figure 3, connect the delivery valves at the lower end of the pump with those on its upper end.

The piston rod 38 has a crosshead 45 which travels in guides 46 and to'a pin 41 carried by this crosshead the upper ends of two links 48 are connected while their lower ends are connected to a pin 49 carried by one pair of ends of the rocking levers 50. The rocking levers 50 are carried on a pin which is pivotally mounted in a bearing 52 and at their other ends these levers are connected to a pin 53 to which the lower ends of links 54 are connected. The upper ends of the links 54 are carried on a pin 55 mounted in the outer ends of two arms 56 which are carried by the centre crosshead I5 of the engine unit 1.

The scavenge pumps I35 and I31 are likewise provided with delivery pipes I55 and I51 connected to the air receiver 32 and are driven by rocking levers connected to the centre crossheads of the engine units 2 and 3 respectively in a similar manner to that above described with reference to the pump 35. w

The sequence of the main cranks of the crankshaft I8 oi the engine is illustrated in Figure 2 and for convenience of identification they are indicated by the numbers of the engine units with which they are associated.

The drives to the three pistons of the pumps 35, I36 and I3! are phased at 120 as will be evident from the crank sequence indicated in Figure 2 and by making the working parts of all three pumps identical, there is complete balance of the primary and secondary vertical forces, and there is therefore no cross rocking couple.

Small fore and aft rocking couples, both primary and secondary are introduced, but due to the lightness of the parts or the scavenge pumps 35, I36 and I31, their comparatively short stroke and the close proximity of the pump centres tc fine another these couples are of negligible imporance.

With three double-acting pumps 36, I36 and I 31 phased at 120 there are provided six equal chscharges at .60, corresponding with the six scavenging periOds for the cylinders of the engine units 1 to 6. The pressure in the air receiver 32 remains constant during the cycle, thus ensuring equally effective scavenging in the cylinders of the en ine units 1 to 6.

Since the pumps 35, I36 and I31 are of comparatively large bore and are easily accommodated side by side their stroke can be relatively short resulting in low piston speeds, and with ample space available for valves, the air velocities and corresponding pumping losses are low, giving improved mechanical efliciency.

In the event of breakdown of any one of the pumps 35, I35 and I31, the air from the other two is sufiicient to nm the engine at reduced power.

The crank sequence of the engine units instead of being 15-3-6 24 may be 4-2- 63-5, the pumps being connected to the crossheads of the engine units 4, 5 and 6.

This invention provides several advantages over arrangements hitherto used including no increase in overall length of engine; no unbalanced verticaliprimary or secondary vertical forces and no cross rocking couple; no adjustment of reciprocating weights of vertical engine units to obtain balance; uniform air pressure in scavenging air receiver throughout the cycle, giving an equal supply of scavenging air to all cylinders, and resulting in uniform combustion efliciency and reduced fuel consumption; low air-valve velocities with low pumping losses resulting in higher mechanical efliciency of engine, and increased reliability, since two pumps alone would enable the engine to operate at reduced power.

The invention may be applied to six cylinder single-crankshaft internal-combustion engines other than that above described.

It is to be understood that the reference numerals in the claims are merely for the purpose of identifying the positions of the engine units in the engine and the crank sequence and no limitation to the claims is to be implied by the use of such reference numerals therein,

I claim:

1. In a six-cylinder single-crankshaft 2-strokecycle single-acting internal-combustion engine of the opposed-piston vertical type having crossheads operatively connected to said opposed piatons and having engine units numbered 1 to 6 consecutively, said engine units having a crank sequence of 1--5-3--6-2-4, the combination of a plurality of lateral rocking levers, three scavenge pumps of the double-acting type, links operatively connecting said rocking levers to said scavenge pumps, and links operatively connecting said rocking levers to crossheads of engine units numbered 1, 2 and 3. respectively.

2. In a six-cylinder single-crankshaft 2-strokecycle single-acting internal-combustion engine of the opposed-piston vertical type having crossheads operatively connected to said opp sed pistons and having engine units numbered 1 to 6 consecutively, said eng ne units having a crank sequence of 1426-3- 5, the combination of a plurality of lateral rocking levers, three reciprocating scavenge pumps of the double-acting type, links operatively connecting said rocking levers to said scavenge pumps, and links operatively connecting said rocking levers to crossheads of the engine units numbered 4, 5 and 6, respectively. i

3. In a six-cylinder single-crankshaft 2-strokecycle single-acting internal-combustion engine of the opposed-piston vertical type having crossheads operatively connected to said opposed pistons and having engine units numbered 1 to 6 consecutively, said engine units having a crank sequence of 15--3624, the combination of a plurality of sets of rocking levers, three double-acting scavenge pumps having a relatively large bore and short stroke, pistons in said pumps, piston rods formed with crossheads connected to said pump pistons, suction and delivery valves in said pumps, an air receiver in the entablature of said engine, pipes connecting said delivery valves to said receiver, an air intake to which said suction valves are connected, links connecting said rocking lever sets to said pump crossheads, together with links connecting said rocking lever sets to the crossheads of lower opposed pistons of said engine units numbered 1, 2 and 3, respectively.

4. In a six-cylinder single-crankshaft 2-strokecycle single-acting internal-combustion engine of the opposed-piston vertical type having crossheads operatively connected to said opposed pistons and having engine units numbered 1 to 6 consecutively, said engine units having a crank sequence of 1-4-2-6-3-5, the combination of a plurality of sets of rocking levers, three doubleacting scavenge pumps having a relatively large bore and short stroke, pistons in said pumps, piston rods formed with crossheads connected to said pump pistons, suction and delivery valves in said pumps, an air receiver in the entablature of said engine, pipes connecting said delivery valves to said receiver, an air intake to which said suction valves are connected, links connecting said rocking lever sets to said pump crossheads,'together with links connecting said rocking lever sets to the crossheads of said lower opposed pistons of said engine units numbered 4, 5 and 6, respectively.

5. In a six-cylinder single crankshaft intemalcombustion engine having engine units numbered 1 to 6 consecutively and each unit including a cylinder, piston and a crank operatively connected to the piston said units having a crank sequence of 1-5-36-2-4, the combination of three reciprocating scavenge pumps each including a piston and a cylinder, and a plurality of lateral lever driving means'for said pumps operatively connected to engine units numbered 1, 2 and 3 respectively.

6. In a six-cylinder single-crankshaft internalcombustion engine having engine units numbered 1 to 6 consecutively and each unit including a cylinder, piston and a crank operatively connected to the piston said units having a crank sequence of 1-4-2-6-3-5, the combination of three reciprocating scavenge pumps each including a piston and a cylinder and a plurality of and 6 respectively.

'7. In a six-cylinder single-crankshaft internalcombustion engine having engine units numbered 1 to 6 consecutively and each including a cylinder, a piston, a crank, a cross-head and operative connections between the crank and the crosshead and between the cross-head and the piston respectively said engine units having a crank sequence of 14263-5, the combination of three reciprocating scavenge pumps each including a piston and a cylinder and a plurality of lateral lever driving means for said pumps operatively connected to engine units numbered 4, 5 and 6 respectively.

8. In a six-cylinder single-crankshaft 2-stroke cycle single-acting internal-combustion engine of the opposed-piston vertical type having engine units numbered 1 to 6 consecutively and each inlud n a cylinder with two opposed pistons, cranks, cross-heads and operative connections between the cranks and the cross-heads and between the cross-heads and the pistons respectively and said units having a crank sequence of 153-6-2-4, the combination of three reciprocating scavenge pumps each comprising a cylinder and piston, and a plurality of lateral rocking lever means for driving said pumps, said rocking lever driving means being operatively connected to cross-heads associated with one of the opposed pistons of the engine units numbered 1, 2 and 3 respectively.

9. In a six-cylinder single crankshaft 2-stroke cycle single-acting internal-combustion engine of the opposed-piston vertical type having engine units numbered 1 to 6 respectively and each in cluding a cylinder with two opposed pistons, cranks, cross-heads and operative connections between the cranks and the cross-heads and between the cross-heads and the pistons respectively and said units having a crank sequence of 1-42635, the combination of three reciprocating scavenge pumps each comprising a cylinder and a piston and a plurality of lateral rocking lever means for driving said pumps, said rocking lever means being operatively connected to cross-heads associated with one of the opposed pistons of th engine units numbered 4, 5 and 6 respectively.

- WILLIAM HAMILTON PURDIE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Kilehenmann Oct. 3, 1944 

